Amorphous alloys are increasingly used in the fields of horology and jewellery, in particular for the following structures: watch cases, case middles, main plates, bezels, push-buttons, crowns, buckles, bracelets, rings, earrings and others.
Components for external use, intended to be in contact with the user's skin, must obey certain constraints, due, in particular to the toxicity or allergenic effects of some metals, especially beryllium and nickel. Despite the specific intrinsic properties of such metals, endeavours are made to market alloys containing little or no beryllium or nickel, at least for components likely to come into contact with the user's skin.
Zirconium-based solid amorphous alloys have been known since the 1990s. The following publications concern such alloys:
[1] Zhang, et al., Amorphous Zr—Al—TM (TM═Co, Ni, Cu) Alloys with Significant Supercooled Liquid Region of Over 100 K, Materials Transactions, JIM, Vol. 32, No. 11 (1991) pp. 1005-1010.
[2] Lin, et al., Effect of Oxygen Impurity on Crystallization of an Undercooled Bulk Glass Forming Zr—Ti—Cu—Ni—Al Alloy, Materials Transactions, JIM, Vol. 38, No. 5 (1997) pp. 473-477.
[3] U.S. Pat. No 6,592,689.
[4] Inoue, et al., Formation, Thermal Stability and Mechanical Properties of Bulk Glassy Alloys with a Diameter of 20 mm in Zr—(Ti,Nb)—Al—Ni—Cu System, Materials Transactions, JIM, Vol. 50, No. 2 (2009) pp. 388-394.
[5] Zhang, et al., Glass-Forming Ability and Mechanical Properties of the Ternary Cu—Zr—Al and Quaternary Cu—Zr—Al—Ag Bulk Metallic Glasses, Materials Transactions, Vol. 48, No. 7 (2007) pp. 1626-1630.
[6] Inoue, et al., Formation of Icosahedral Quasicristalline Phase in Zr—Al—Ni—Cu—M (M═Ag,Pd,Au or Pt) Systems, Materials Transactions, JIM, Vol. 40, No. 10 (1999) pp. 1181-1184.
[7] Inoue, et al., Effect of Additional Elements on Glass transition Behavior and Glass Formation tendency of Zr—Al—Cu—Ni Alloys, Materials Transactions, JIM, Vol. 36, No. 12 (1995) pp. 1420-1426.
Amorphous alloys with the best glass forming ability, known as and referred to hereafter as “GFA”, are found in the following systems:                Zr—Ti—Cu—Ni—Be (for example LM1b, Zr44Ti11Cu9.8Ni10.2Be25),        and Zr—Cu—Ni—Al.        
Given the toxicity of beryllium, alloys containing beryllium cannot be used for applications involving contact with skin, such as external watch parts or suchlike. However, zirconium-based, beryllium free amorphous alloys generally exhibit a critical diameter which is lower than that of alloys containing beryllium, which is unfavourable for making solid parts. The best composition in terms of critical diameter (Dc) and the difference ΔTx between the crystallisation temperature Tx and the vitreous transition temperature Tg (supercooled liquid region) in the Zr—Cu—Ni—Al system is the alloy Zr65Cu17.5Ni10Al7.5 [1].
Modifications are also known wherein the GFA has been improved by adding titanium and/or niobium:                Zr52.5Cu17.9Ni14.6Al10Ti5 (Vit105) [2]        Zr57Cu15.4Ni12.6Al10Nb5 (Vit106) and Zr58.5CU15.6Ni12.8Al10.3Nb2.8 (Vit106a) [3]        Zr61Cu17.5Ni10Al7.5Ti2Nb2 [4]        
In general, the addition of titanium and/or niobium increases the critical diameter of alloys, however the modification greatly decreases the gradient ΔTx and therefore the process window for any hot deformation of such alloys. Further, given its very high melting temperature (2468° C.), niobium is not easy to melt, which complicates fabrication of a homogeneous alloy.
It is also known that adding silver to ternary Zr—Cr—Al alloys increases critical diameter, especially for modifications of the composition Zr46Cu46Al8, for example Zr42Cu42Al8Ag8 [5].
However, due to the high level of copper and the absence of nickel, these alloys are not very resistant to corrosion and even tend to become discoloured (and/or turn black) over time at ambient temperature.
Further, it is known that adding more than 5% silver, gold, palladium or platinum to Zr—Cu—Ni—Al amorphous alloys stimulates the formation of quasicrystals during devitrification of such alloys by a heat treatment between Tg and Tx [6].
In publication [7], the effect of an additional element M (M═Ti, Hf, V, Nb, Cr, Mo, Fe, Co, Pd or Ag) on the GFA of a Zr—Cu—Ni—Al—M alloy was tested.
The results demonstrate that only titanium, niobium and palladium increase the critical diameter of the alloy, yet also greatly decrease the gradient ΔTx. No particular effect is cited as regards the addition of silver to the alloy.
The documents below include zirconium based alloys with silver or gold.
U.S. Pat. Nos. 5,980,652 and 5,803,996 describe alloys of the following type:    Zrbar-(Ti, Hf,Al,Ga)5-20-(Fe, Co, Ni,Cu)20-40-(Pd, Pt,Au,Ag)0-10 and more particularly alloys with palladium and/or platinum, a single example citing the addition of 1% gold or 1% silver, with no evaluation of the effect of this addition on the increase in critical diameter.
EP Patent No 0905268 describes alloys of the following type:    (Zr, Hf)25-85-(Ni, Cu, Fe, Co, Mn)5-70-Al0-35-T>0-15 where T is an element with a negative enthalpy of mixing with one of the other elements, and is chosen from the following group: T═Ru, Os, Rh, Ir, Pd, Pt, V, Nb, Ta, Cr, Mo, W, Au, Ga, Ge, Re, Si, Sn or Ti. This document only gives one example with palladium. It does not demonstrate any positive effect of elements T on Dc and ΔTx.
EP Patent No 0905269 describes a method of manufacturing a multi-phase alloy (14-23% crystalline phase in an amorphous matrix) by a heat treatment of Zr25-85-(Ni,Cu)5-70-Al>0-35-Ag>0-15.
CN Patent No 101314838 describes alloys of the following type:    Zr41-63-Cu18-46-Ni1.5-12.5-Al4-15-Ag1.5-26 
In short, little is known about the effects of adding a low concentration of silver or gold to such amorphous alloys, and such effects have not been subject to any particular investigation in the literature.